1. The American College of Obstetricians and Gynecologists (ACOG). Women’s Health Care
Physicians. Your Pregnancy and Childbirth: Month to Month. Revised 6th edition. (Washington, D.C.: American College of Obstetricians and Gynecologists, 2016), 212-213. Print Edition.

2. The Pregnancy Experts at Mayo Clinic. Medical editors: Roger Harms, MD, Myra Wick, MD, PhD. Mayo Clinic Guide to a Health Pregnancy. (Boston, Massachusetts: Mayo Foundation for Medical Education and Research, 2011), 200-201. Print Edition.

3. Hakakha, Michele M.D and Ari Brown, M.D. Expecting 411: Clear Answers & Smart Advice for Your Pregnancy. (Boulder, Colorado: Windsor Peak Press, 2019), 280. Print Edition.